title: Ethacrynic acid oxadiazole analogs induce apoptosis in malignant hematologic cells through downregulation of Mcl-1 and c-FLIP, which was attenuated by GSTP1-1.
abstract: Ethacrynic acid, a diuretic, inhibits glutathione S-transferase P1-1 (GSTP1-1) activity and induces cell death in malignant cells at high concentrations. To improve ethacrynic acid activity, ethacrynic acid oxadiazole analogs 6s and 6u were synthesized. Although both compounds have greater antiproliferative effects than ethacrynic acid in human HL-60 cells, 6u has a reduced ability to inhibit GSTP1-1 activity. The mechanisms of both 6s- and 6u-induced cell death as well as the role of GSTP1-1 in their actions were studied. Both 6s and 6u equally induced apoptosis in HL-60 cells due to the activation of caspase-3, -9, and -8, which was correlated with the downregulation of antiapoptotic proteins c-FLIP, Mcl-1, and XIAP. The caspase inhibitor Z-VAD-FMK blocked the reduction of XIAP, but not of c-FLIP and Mcl-1, in 6s-treated cells. The reduction of c-FLIP and Mcl-1 by 6s was not blocked by the proteasomal inhibitor MG132, but was correlated with inhibition of the phosphorylation of extracellular signal-regulated kinase (ERK) and eIF4E. Both 6s and 6u decreased the intracellular glutathione (GSH) levels. N-acetylcysteine blocked reduction in the levels of Mcl-1, c-FLIP, and intracellular GSH as well as apoptosis in HL-60 cells treated by either compound. Silencing of GSTP1-1 in K562 cells sensitized, but overexpression of GSTP1-1 in Raji cells blocked, apoptosis induction by either compound. GSH conjugation at the methylene group abrogated the ability of inducing apoptosis. These data suggest that the methylene group plays an important role in the downregulation of c-FLIP and Mcl-1 proteins and apoptosis induction, which is inactivated by GSTP1-1 by forming GSH conjugates.
authors.affiliation: Corresponding Author: Yongkui Jing, Division of Hematology/Oncology, Department of Medicine, Box 1178, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029-6547. yongkui.jing@mssm.edu.
authors.forename: Guyue
authors.initials: G
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Yuetong
authors.initials: Y
authors.lastname: Wang
authors.forename: Pengzhan
authors.initials: P
authors.lastname: Li
authors.forename: Guisen
authors.initials: G
authors.lastname: Zhao
authors.forename: Linxiang
authors.initials: L
authors.lastname: Zhao
authors.forename: Yongkui
authors.initials: Y
authors.lastname: Jing
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism*; D020169:Caspases / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004976:Ethacrynic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D015973:Gene Expression Regulation, Leukemic; D005978:Glutathione / Q000378:metabolism; D051549:Glutathione S-Transferase pi / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D019169:Jurkat Cells; D020014:K562 Cells; D007951:Leukemia, Myeloid / Q000473:pathology*; D007976:Leupeptins / Q000494:pharmacology; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000235:genetics / Q000378:metabolism*; D010069:Oxadiazoles / Q000737:chemistry / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: C587438:1-(2,3-dichloro-4-((3-(4-(trifluoromethyl)phenyl)-1,2,4-oxadiazol-5-yl)methoxy)phenyl)-2-methylenebutan-1-one; C587437:1-(2,3-dichloro-4-((3-phenyl-1,2,4-oxadiazol-5-yl)methoxy)phenyl)-2-methylenebutan-1-one; D000590:Amino Acid Chloromethyl Ketones; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D004791:Enzyme Inhibitors; D007976:Leupeptins; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010069:Oxadiazoles; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D020169:Caspases; D005978:Glutathione; D004976:Ethacrynic Acid; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde